It has been well known that photographic emulsions are affected during preservation or by surrounding conditions in case of development to form a detectable amount of metal silver called fog on unexposed parts. Generation of the fog is accelerated not only under bad conditions during preservation but also under bad conditions during development. When they are exposed to air in a state of wetting with a developing solution in case of development, the fog is particularly vigorously generated, which is generally called "aerial fog".
With respect to the fog, a presumptive mechanism of generation of the fog and acceleration of aerial fog in the presence of copper or iron have been described in "Stabilization of Photographic Silver Halide Emulsions", written by E. J. Birr, published by Focal Press, 1974, pages 128-129, and, further, a method restraining the fog has been described therein.
In order to prevent such aerial fog, it has been proposed to use amide and oxime compounds described in British Pat. Nos. 988,052, 623,448 and 1,057,470 (corresponding to U.S. Pat. No. 3,393,072) cited in the above described literature. However, many of these compounds are not satisfactory, because their effect is poor or the effect remarkably deteriorates after preservation of the light-sensitive materials at a high temperature and a high humidity, even if it is excellent at first. Alternatively, they cause side reactions with a hardener in the gelatin film to result in bad influences such as deterioration of quality of the gelatin film.
It has been described in U.S. Pat. No. 3,193,386 that safety with respect to a safe light is improved and black spot fog can be prevented by using 8-hydroxyquinoline which resembles the compound of the present invention together with 8-hydroxyquinoline-5-sulfonic acid. However, the effect is insufficient, even though 8-hydroxyquinoline has some ability to prevent aerial fog by itself as shown in the example.
Accordingly, it has been desired to use aerial antifogging agents which do not have the bad effects and are effective for a long period of time. Further, in recent years, it has been desired to use antifogging agents which have stronger effects, because high temperature development or quick development is often carried out which increases the degree of fog due to the faster processing.